(WASHINGTON, D.C.) — Members of the Congressional Republican leadership, along with Republican leaders of the Appropriations, Finance and Ways and Means Committees, called on the new Commissioner of the IRS to abandon a proposed rule designed to muzzle the free speech rights of groups critical of the Obama administration.

“It is our view that finalizing this proposed rule would make intimidation and harassment of the administration’s political opponents the official policy of the IRS and would allow the Obama Administration to use your agency as a partisan tool. This would be a serious error, especially in light of the recent track record of intimidation at the IRS. It would also cement your reputation as someone who is unable or unwilling to restore the public’s faith in this important agency,” according to the letter addressed to IRS Commissioner John Koskinen.

Referring to the IRS targeting of conservative groups in the run-up to the 2010 and 2012 elections, the lawmakers wrote that the proposed new rule continues the agency’s targeting of First Amendment rights by these same grass-root conservative groups.

“This rule would redefine political activity so broadly that grass-roots groups all across the country will likely be forced to shut down simply for engaging in the kind of non-partisan educational activities” their tax designation was designed to support, the letter said. “In many cases, these are the same groups that were already victimized by the IRS’s inappropriate targeting.”

The top Republican lawmakers wrote that the proposed rule appears calculated to take effect just in time for the mid-term elections, giving a “strong appearance” of political motivation.

“This proposed rule is an affront to free speech itself,” the letter said. “It poses a serious and undeniable threat to the ability of ordinary Americans to freely participate in the democratic process. That’s why groups all along the political spectrum, from the ACLU to the Chamber of Commerce, and the citizens who support them, are increasingly concerned about its effect.”

Noting that the recently confirmed IRS Commissioner John Koskinen inherited the proposed rule from his predecessor, the letter said that Koskinen now faces a choice of either withdrawing the proposed rule or allowing the Obama Administration “to use the agency as a means to infringe on the constitutionally protected right to free speech.”

“One of the reasons you have been appointed to a five-year term is so that you will be protected from undue political pressure. So, we urge you to take a stand against this kind of intimidation, abandon this proposed rule, and make it clear to a nervous public that your agency will no longer engage in government-sanctioned crackdowns on speech,” the lawmakers wrote.